The invention relates to an adjustable continuous casting mould for manufacturing continuously cast ingots of different dimensions, having a mould frame with a pair of stationary facing side walls and a pair of facing end walls, where at least one end wall can be displaced and each side wall and end wall features a primary coolant chamber and, connected to the primary coolant chamber, a plurality of primary coolant channels for jetting coolant onto the ingot material. The invention also relates to a process for carrying out the continuous casting process with the mould according to the invention.
Continuous casting moulds are used for casting molten metal from a crucible or the like into a given shape; this enables ingots of full or hollow cross-section to be produced. Such continuous casting devices for producing ingots or billets as starting material for further processing, e.g. by extrusion or rolling, comprise a water-cooled mould i.e. a mould which is normally open at the top having parallel walls and a dummy base which initially seals off the mould bottom but can be lowered, the mould walls normally being hollow and filled with water
During continuous casting, molten metal is cast at a given rate onto a dummy base which initially forms a seal with the mould frame. The mould frame forms the container for the melt and must therefore be tightly sealed around the whole of its periphery. During the casting process the mould base is lowered and at the same time sufficient molten metal poured into the mould as is required to keep the level of metal there constant. The mould base is therefore lowered at a rate which conforms with the rate of casting.
The mould frame provides the shape of the ingot and, at the same time removes the heat from the melt. When the metal is poured into the mould, the metal solidifies rapidly on the walls and base of the mould, so that at least the outermost edge zone of the melt solidifies within the mould frame. By jetting the ingot emerging from the frame with a coolant, e.g. spraying water onto the ingot, more of the region close to the surface of the ingot emerging from the mould solidifies rapidly with the result that a cup--the contents of which are still liquid--is formed.
When continuous casting metal rolling ingots and such cast blocks, it is normal to employ a special mould for each ingot width. Mainly because of the close dimensional tolerances required, it is complicated and expensive to produce continuous casting moulds. As many different ingot formats are required, it is necessary and uneconomical to keep a corresponding large number of moulds in store.
In order to reduce this problem at least in part, it has been proposed in the German patent document 1 059 626 to produce cast blocks of elongated cross-section by employing a mould comprising a closed ring with parallel side and end walls in which at least one end wall can be displaced within the closed ring. The adjustable wall is set to the desired ingot cross-section prior to casting, the adjustable walls being attached by screws to the rest of the frame.
The mould according to the German patent document 1 059 626 is, however, such that the dummy base of the mould has to be adjusted each time to suit the new ingot cross-section Also, the adjustment of the mould frame to the desired cross-section is very time consuming and normally leads to a long interruption in the production line. This has an unfavourable influence on production time and production costs, especially if only few cast lengths of a particular width are required.
In order to eliminate this disadvantage the patent document FR-83 15766, published under number 2 552 692, describes a mould with a cross-section which may be adjusted during continuous casting, the desired effect being achieved by computer controlled change of inclination of an adjustable end wall. The amount of computer calculation necessary for such control of the cross-section is, however, large--which makes it necessary to employ high powered computer facilities.
During continuous casting the solid edge zone of metal formed in the mould must be able to withstand the total pressure of the ingot material above it also when the ingot has emerged from the mould. The said total pressure comprises the hydrostatic pressure of molten metal and the pressure of the metal already solidified at a higher level. Whereas in the case of stationary vertical mould walls the total pressure acting on the surface of the edge zone depends solely on the hydrostatic pressure of the melt, the total pressure on ingots which are emerging from the mould and do not exhibit a vertical edge zone is determined also by the components of the solidified metal above acting vertically onto the edge zone. Consequently, in the case of moulds with walls that are adjustable during the continuous casting process, the rate of adjusting the mould cross-section to the desired ingot cross-section--especially when increasing the cross-section--depends on the material being cast and on the thickness of the solidified edge zone. In order to avoid scrap, the casting process is preferably started with the adjustable mould at a smaller cross-section than the desired ingot cross-section and the cross-section gradually adjusted accordingly. As a result, because of the thin ingot edge zone formed in the mould, the maximum rate of adjusting the mould cross-section is normally very small. This has a corresponding negative effect especially if a large change in cross-section is required, resulting in a large loss of material as the part of the ingot over which the cross-section varies is usually not suitable for further processing.